Microporous Diaphragm Aerator Improves Flue Gas CO2 Dissolution and Photosynthetic Characteristics of Arthrospira Cells in 660 m2 Raceway Ponds

The flue gas CO2 from coal chemical plants can be purified and then absorbed by microalgae to produce high valued products and achieve CO2 emission reduction. The dissolution of CO2 from coal chemical flue gas was strengthened using microporous diaphragm aerators (MDA) to promote the HCO3- concentration for improving photosynthetic characteristics of Arthrospira cells in 660 m(2) raceway ponds with 2.5-10 vol % CO2 gas. An increase in the quantum yield of the photosynthetic electron transfer of Arthrospira cells promoted biomass growth by 15.5% in the MDA-equipped raceway pond. The specific energy fluxes of light absorption (ABS/RC) and electron transport (ET0/RC) in Arthrospira cells at 23 h first increased to peaks of 3113 and 757, respectively, when the CO2 concentration increased from 0.04% (air) to 7.5 vol %, and then both values decreased when the CO2 concentration further increased to 10 vol %. Accordingly, the photosystem II (PSII) reaction center quantity and the driving force per excited cross-section reached peaks of 628 and 2.72, respectively, at 7.5 vol % CO2. Therefore, the Arthrospira carotenoid yield increased by 25% and peaked when the CO2 concentration increased from 0.04% (air) to 7.5 vol %. This could provide guidance for engineering demonstration of large-scale microalgae cultivation.